The present invention relates to a photographing apparatus, and more specifically to an endoscopic photographing apparatus for photographing an endoscopic image.
In conventional endoscopic photographing apparatuses, three-primary-color image signals are delivered successively from a CCD pickup device, at intervals of 1/90 second, according to the frame-sequential system. After they are subjected to analog-to-digital conversion, the signals are stored individually in R, G and B pre-stage frame memories. The R, G and B image signals from the pre-stage memories are then transferred to and stored in R, G and B post-stage frame memories, respectively. While the pre-stage memories are engaged in writing operation, the image signals cannot be written in the post-stage memories. The image signals from the pre-stage memories are partially transferred to and stored in their corresponding post-stage memories, at the same time, during the period between the end of the successive storage in one of the pre-stage memories, and the start of storage in the subsequent frame memory. Thus, the image signals are stored in the post-stage memories, while being partially rewritten at intervals of 1/90 second. The image signals R, G and B, stored in the R, G and B post-stage frame memories, are read out simultaneously at intervals of 1/30 second, in synchronism with television synchronizing signals, and displayed as a color picture on a monitor.
According to the prior art photographing apparatus, the post-stage frame memories are partially rewritten with every 1/60 second in monochro picture mode, and then if the subject moves quickly, the image is displayed separated in up and down. That is, as shown in FIG. 14A, when a subject moves from f0 to f1, the upper half of image f0 and the lower half of image f1 are displayed as on frame as shown in f0/f1. In color picture, the post-stage frame memories are partially rewrited with every 1/90 second. In this case, when the subject moves from one position (f0) to the other position (f1), each of R, G, and B images changes to f0, f0/f1, f0/f1 and f1 in this order as shown in FIG. 14B. When the three fundamental color images R, G, and B represented by f0/f1 and f0/f1 are combined to obtain a color picture, the color picture is displayed as an RGB image with color breakup. Such display picture will be a substantial offense to the eye, suffering flickers.